Fluent fuel burner



Patented July 31, 1945 V FLUENT roar. nuance Arthur J Poole, Belleville,N. 1., asslgnor to The Babcock.& Wilcox Company, Jersey City, N. J., acorporation of New Jersey Application June 23, 1942, Serial No. 448,061

11 Claims. (C

' stream are provided, and each division separately The inventiondisclosed herein relates-particu larly to burners utilizing a fuel whichis capable of being projected into the combustion zone in a fluentstream. A specific application of the invention is in connection withpulverized fuel burners of the circular type arranged to discharge afluent mixture of solid fuel particles and primary air from a centralburner pipe or nozzle,

and to discharge additional. secondary air an nularly of the pipe, thefuel-air mixture being mingled with the secondary air in suitableproportions to insure complete combustion.

deflected and dispersed, such components being of a form facilitatingeconomical manufacture and assembly, and being so arranged that they maybe protected from overheating as a result of their exposure to radiantheat from the furnace.

An important consideration, as is well known,

is to provide even distribution of the fuel particles throughout themixture entering the furnace. and to provide sufficient dispersion ofthe entering fuel-air stream to promote thorough mingling with thesupply of secondary air. In circular pulverized fuel burners, asheretofore constructed, it has been common practice to employ a bladedmember opposite the nozzle outlet for dividing the fuel-air mixturecircumferentially while imparting a rotational deflection, thus tendingto cause the solid fuel particles to be thrown outwardly by centrifugalforce into the surrounding body of secondary air.

The present invention has for an object an improvement in circular fuelburners wherein dispersion of the fluent fuel stream is effecteddirectly by deflecting portions outwardly into the secondary air stream.Since the fuel is discharged from the burner at a considerably highervelocity than the surrounding annulus'of secondary air. the deflectionis made from a zone of relatively high pressure to a zone of relativelylower pressure. so that there is penetration of the deflected fuel intothe combustion air to produce turbulence, thereby promoting thoroughmixing without the supplemental whirling action inherent in other burnerconstructions.

Another object contemplates improved distribution of fuel throughout theentering fuel-air mixture as contributory to thorough mixing of the fuelwith the total combustion air supply,-

for improved ignition and complete combustion.

In view of the abrasive character of pulverulent fuels. and ofpulverized coal in particular. a more specific object pertains to animproved dispersing means, herein termed an impeller, capable ofproviding the desired deflection of the fuel into the surroundingcombustion air with minimum erosion of-the impeller structure.

It is further proposed to utilize an impeller having annular componentsconcentrically ar-' ranged so that annular divisions of the, fluentOther objects and advantages will be apparent as the descriptionproceeds in more detail, particularly when read in conjunction with theaccompanying drawing, in which:

- Fig. l is a sectional assembly view of fuel burning apparatusembodying various features of the invention;

Fig. 2 is a fragmentary enlargement of parts shown in Fig. l; and,

Fig. 3 is an end projection of Fig. 2.

In detail, according to Fig. l of the drawing, a fuel burner is shown inassociation with a furnace wall l0 forming a boundary for a combustionzone i2 at one side, the burner being arranged to deliver fuel and airthrough a burner opening or port I having circumferential wall surfacesl8 and i8 converging inwardly to form a venturilike passage providing aburner throat 20 of restricted diameter at an intermediate location.

The burner includes a fuel pipe or tube 22 having a cylindrical nozzleportion 24 mounted axially of the opening with its circular fueldischarge outlet 26 positioned adjacent the throat portion 20, a portion28 being formed as an elbow zle portion 24, so that the entering fuelstriking the inclined inner surface of the cover plate 34 at an angle ofabout or more tends to produce a turbulence which effects aredistribution of the 1 fuel particles throughout the mixture to providea cylindrical casing" in which movable vanes 84 arearranged, preferablyuniformly distributed in an annular series, for regulating the supply ofsecondary air delivered to and through the burner throat 20, thevanesbeing suitably mounted for angular adjustment about radially extendingaxes, as indicated by the broken lines, whereby in addition to effectingregulation of the amount of secondary air supplied, the vanes impart adegree of. rotation to the annular air stream. The extent of adjustmentof the vanes 44 is under control of the handle 46 located exteriorly ofthe casing 36 and forming part of a suitable operating mechanism,

The mixture of fuel and air as it is discharged from the circular outlet26 is deflected and simultaneously dispersed into intimate minglingrelation with the supply of secondary air entering the combustion zonethrough the annular passage 66 formed between the cylindrical .bumer pipportion 2| and the surrounding converging wall por tion of the burneropening ll.

The deflecting-dispersing device 66, which for convenience may be termedan impeller, is -mounted axially of the discharge outlet 26 andcomprises a series of annular vanes, in the present embodiment threevanes 62-, 66 and 66 being utilized, each formed substantially as thefrustum of a hollow cone having its vertex at the sidetoward th fueloutlet 26. The vanes are supported in concentric spaced relation bymeans of ribs 66 arranged radially which are circumferentially spacedabout the hub 66 to which they are secured, as indicated, the hub 66being open at both ends and telescoping over the outlet end of a tubularsupporting member 62 to which it is adiustably secured as by one or moreset screws 66.

The hub 66 is preferably beveled as at 66 to minimize resistance to theflow of the fuel-air mixture. Pins 66 extending outwardly from the theinnermost vane 62 having an inside diameter approximately equal to theoutside diameter of the hub 66 and its inner circumferential edge spacedlongitudinally from the end of th hub; the outermost vane 66 having. anoutside diameter less than the inside diameter of the nozzle outlet 26to provide a clearance space permitting withdrawal of the impeller 66through the nozzle 26 into the elbow 26 for removal through th accessopening 32. The outer edges of the vanes may also lie at the surface ofa cone having its vertex at the side remotefrom the outlet 26, and withvanes of equal widths, at equal spacings, the angularity of the conescontaining the inner and outer edges is approximately 45 with respect tothe central axis, the same as the angularity of the cones determiningthe conical surfaces of the vanes. The vanes are also so proportionedand arranged as to provide a small amount of overlap longitudinally andradially between adjacent vanes, the radial overlap being usually thesmaller and an amount not exceeding 5 one-hundredths of an inch fordiameters up to about 12 inches generally being sufficient to assuredeflection of the entire fuel stream.

, central axis.

member 62 bear against the inner wall of the pipe 26 and serve tosupport the member and thereby the impeller 66 in centralized relationto the pipe. I The member 62 also has a bearing in the extension 76 onthe cover plate 36, a handle 14 being provided at the outer end of themember for convenience'in moving the impeller 60 longitudinally of thepipe 24 into and out of position relative to the outlet 26, and a,set'screw 12 provided for *surfaces'and the vane 56 nearest the fuel outlet26, at approximately the same distance from the inner end of the nozzle24. The space between blades and-from the end of the nozzle may beadjusted to suit particular operating conditions and/or thecharacteristics of the fuel being used; for example, when the fuel 'is agas. it will probably be. ,found more desirable to reduce the amount Ofspacing, as compared with the amount I used with the usual fluentmixture of pulyerized coal and air. The vanes may be of equal widths. asshown, and of equal angularity with respect to their common centralaxis, a suitable angularity having been found to be about'45, asillustrated in Fig. 2, although other values of angularity may beutilized, either higher or lower.

The vanes are of progressively decreasing diameters. inside and outside,advancing from-the outlet 26 of nozzl 24, the inner circumferential edgebeing shown of uniformly decreasing diam- In the operation of the burnerdescribed, the fluent mixture of fuel and primary air is discharged inan annular stream from the nozzle outlet 26, and is successively dividedinto concentric annular portions, first by the outermost vane 66 whichremoves the outer layer from the annular fuel-air column and deflectsthat portion outwardly in the form of a hollow cone into the supply ofsecondary air entering through the throat 20. The remaining centralportion of the fuel-air stream is then further divided by the nextsmaller vane 56 providing additional annular layers which are similarlydeflected outwardly into the secondary air stream in the form of hollowcones by the conical vanes '64 and 52, respectively. a

With the vane surfaces inclined at an anal of about.45, for example. tothe axial flow of the fuel-airstream, the resulting angularity of flowis sufficiently abrupt in relation to the flow of secondary air toproduce turbulence, and since each vane deflects a separate annulardivision of the stream in the direction of a. different zone ofsecondary air, such turbulence assures intimate mingling of each unit offuel. with the required proportion of combustion air. Thus, thesuccessive dividing and deflecting of the fuel-air mixture is effectivein providing the degree of dispersion and turbulence essential forcomplete diets and thus lying at the surface of a cone hava in; itsvertex at the side remote from the outlet;

combustion of individual divisions, and thercb of the entire fuelsupply, and moreover accomplishes these results by a direct expansion ofthe perimeter of successive portions without relying on centrifugalforce to throw the'fuel particles outwardly as in the case of bladeswhich in de-.

fleeting the fuel circumferentially tend to impart a swirling movementto the discharging fuel. Furthermore, after extended periods of use. ithas been indicated that there is less erosion of the conical deflectorvanes than of other forms of deflector elements, with the result thatthe serviceable life .of such parts has been substanaae cee 3 1 tiallyprolonged,"and thecost of impeller maintenance accordingly reduced. Theconical form of the vanes also has the advantage of resistingdeformation due to heat, while if a slightwarp should occur there wouldordinarily be no diffl-' 5 culty in withdrawing the impeller through andfrom the 'pipe 22 for inspection or replacement due to therecedinginclination of the vane surfaces.

The outer open end of the tubular member 62 v. of the member, some ofthe air being discharged axially within the vane and some mingling withfuel passing between the vanes 52 and 54. Air admitted through member 62in this manner serves as a coolant for the vanes and for the exposed endof the hub, and has also been found beneficial in certain instances and,with certain coals in obviating or at least minimizing minor cokeformations within the member 62 or on the innermost vane 52 where thetendency for such 2 formations might sometimes occur.

' If desired, an oil atomizer of suitable type may be assembled withinthe tubular member 62, with its tip adjacent the end of hub 60, similarto the arrangement disclosed in U. S. Patent 1,994,461, E. L. Boland,for burning oil, either alone or in combination with the fuel dischargedthrough the nozzle 24.

While in accordance with the provisions of the statutes I haveillustrated and. described herein the best forms of my invention nowknown to me, those skilled in the art will understand that changes maybe made in the form of the apparatus disclosed without departing fromthe spirit of the invention covered by my claims, and that certainfeatures of my invention may sometimes be used to advantage without acorresponding use of other features.

I claim:

1. In a burner arranged to discharge fluent fuel and air through afurnace wall opening, said opening being of circular cross-sectionthroughout and of tapering cross-section inwardly from its ends toprovide an intermediate throat portion of restricted diameter, a burnernozzle having an,

outlet at one end adjacent said throat portion for discharging said fuelin an annular stream axially of said opening, said burner nozzle .andthe surrounding wall portion of said opening defining an annular passagefor combustion air of gradually decreasing "diameter and cross-section,.said annular passage having its outlet substantially within said throatportion, means for reg- 'ulating the flow of combustion air through saidpassage while imparting a-whirling motion to said air flow, and animpeller opposite said nozzle outlet for dispersing said fuel intointimate mingling relation with said combustion air, said impellercomprising means for successively dividmg said stream of fuel intoconcentric annular cur- 5 rents and for directing said currentsoutwardly at substantially equal angles oblique to the axial directionof flow from said nozzle outlet, said last named means comprising aseries of stationary axially spaced annular vanes terminating in freeinner and free outer circumferential edges of which said free inneredges are of diameters less than the diameter of said outlet and ofprogressively decreasing diameters at progressivelyincreasing distancesfrom said outlet.

2. In a burner arranged to discharge fluent fuel and air through acircular furnace wall opening having an intermediate throat portion ofre-,- stricted diameter, a burner nozzle having an outlet atone end fordischarging said fuel in an ann'ular stream axially of said throatportion, means for discharging combustion air through said throatportion annularly of said fuel discharge outlet, an impeller oppositesaid fuel discharge outlet for dispersing said fuel into said combos--tion air, said impeller comprising stationary vanes of substantiallyfrusto-conical form arranged concentricallyin spaced nested relation fordividing and directing theflow of fuel from said ,outlet to provideexpanding annular streams, a tubular member telescoped within saidburner nozzle for supporting said impeller and for making adjustments inthe position of said impeller vanes relative to said nozzle outlet andthroat portion, successive vanes terminating in inner edges ofprogressively decreasing diameters in the direction of flow from saidoutlet, the innermost of said nested vanes having its inner edge spacedfrom the exposed end of said member while in substantial. alignment withthe perimeter thereof, and

means for inducing a flow of air through the in- 'terior of said membe'rfor cooling the exposed adjacent surfaces of said member and innermostvane.

3, In a fluent fuel burner, a burner tube having a fuel discharge outletof annular formation at one end, means for directing combustion airlongitudinally of said tube and past said outlet end in an annularstream uniformly distributed about said tube, and means arrangedconcentrically with said tube for successively dividing the dischargingfuel into concentric annular streams and for directing each of saidstreams outwardly with respect to the central axi of said tube intointersecting relation with said annular stream of combustion air, saidlast named means comprising a series of spaced annular vanes each havinga free inner and a free outer circumferential edge and being ofcontinuously flaring formation from its inner circumferential edge toits outer, said inner edges being of progressively decreasing diametersat progressively greater distances from said outlet, each of said vanesbeing relatively narrow with respect, to its mean diameter andsuccessive vanes being arranged in longitudinally overlapping relationto form a compact series of 4. In a fluent fuel burner, a burner tubehaving an outlet at one end arranged to discharge fuel in an annularstream, fuel dispersing means arranged coaxially With said outlet forsuccessively dividing the discharging fuel into concentrican- .nula'rstreams and for directing each of said streams outwardly with respect tothe central axis of said. tube in the form of a hollow cone, said meanscomprising a series of concentric annular vanes successively spaced fromsaid outlet, said vanes terminating in free innerand freeouter'circumferenti-al edges and each being formed in thecircumferential edges being of progressively decreasing diameters atprogressively greater dis-' 'tances from said outlet. each of said vanesbe ng relatively narrow by several times with respect to its meandiameter and successive vanes being arranged in longitudinallyoverlapping relation to form a compact series of said vanes extendinglongitudinally from said outlet a distance less than the mean diameterof said outlet, and means for supplying combustion air in an anularcolumn uniformly distributed about said outlet and said series of vanes.V

5. In combination with a furnace wall having a fuel burner openingtherein, a burner tube ar ranged axially of said opening for dischargingfluent fuel therethrough, said burner tube terminatingin an outletwithin said opening and having internal displacer means for causing saidfuel to be discharged in an annular'stream, means for dispersing saidfuel upon discharge from said outlet, and means for supplying combustionair through said opening annularly of said dispersing' means, saiddispersing means comprising a series of conically formed rings arrangedin concentric nested relation for successively dividing said stream offuel into concentric annular layers and for directing said layersoutwardly into said annulus of combustion air each in the form of ahollow cone, successive rings terminating in free inner circumferentialedges of progressively decreasing diameters at locations progressivelyfarther from said outlet, the ring of minimum diameter having its freeinner edge substantially coincident with the periphery of said displacermeans and said series of rings terminating short of the furnace end ofsaid fuel burner opening.

6. In combination with a furnace wall having a fuel burner port ofcircular cross section therein, a fuel burner nozzle disposed axially ofsaid port and terminating in an annular outlet within said port fordischarging fluent fuel therethrough, said burner nozzle being of adiameter less than the diameter of said port to provide a surroundingannular passage for combustion air, and means opposite said nozzleoutlet and within said port for dispersing said fuel into thesurrounding annular body of said combustion air, said dispersingmeans-comprising a series of spaced rings of truncated conical formarranged concentrically in nested relation, said rings being formedrelative to vertices at the side toward said nozzle and terminating infree inner and free outer circumferential edges, said free inner edgeshaving diameters less than the maximum diameter of said annular outletand lying at the surface of a cone having its vertex at the side remotefrom said nozzle, said series of nested rings extending axially fromsaid nozzle outlet a distance less than the distance between said outletand the furnace end of said fuel burner port 7. In combination with afurnace wall having a fuel burner port of circular cross sectiontherein, said port having a circumferential wall portion taperinginwardly from its outer end to provide an opening of reduced crosssection intermediate the ends of said port, a fuel burner nozzledisposed axially of said port and terminating in an annular outletadjacent said opening of reduced cross section for discharging fluentfuel through said port, said nozzle being of a diameter less than thediamgressively decreasing diameters at progressively increasinglongitudinal distances from said outlet, said free inner edges havingdiameters less than the maximum diameter of said outlet, each vane beingrelatively narrow in relation to its mean diameter and successive vanesbeing arranged in longitudinally overlapping relations to provide aseries of vanes disposed wholly between said outlet and the furnace endof said fuel burner port. v

8. In combination with a furnace wall having a fuel burner port ofcircular cross section therein, a fuel burner nozzle disposed axially ofsaid port for discharging fluent fuel therethrough, said nozzleterminating within said port in an annular outlet spaced from thefurnace end of said port, said nozzle being of a diameter less than thediameter of said port to provide a surrounding passage for supplyingcombustion air annularly of said outlet, and means for directing saidfuel into said annularly supplied combustion air comprising a series ofannularvanes arranged concentrically in longitudinally spaced successionfrom said outlet, successive vanes terminating in free inner and freeouter circumferential edges of progressively decreasing diametersadvancing from said outlet, each vane being relatively narrow inrelation to its mean diameter and being of continuously flaringformation from its inner to its outer circumferential'edge with saidouter edge leading said inner edge,.said vanes being spaced from eachother and from the periphery of said outlet in substantially equalamounts'in a direction normal to said vanes, successive vanes beingarranged in overlapping relation radially and longitudinally to anextent providing a lesser amount of overlap in the radial direction,said series of vanes extending axially from said outlet a distance lessthan the diameter of said outlet and terminating short of the furnaceend of said fuel burner port.

9. In a fluent fuel burner, a burner tube having an outlet at one endarranged to discharge fuel in an annular stream, fuel dispersing meansarranged coaxially with said outlet for dividing the discharging fuelinto concentric annular portions and for directing each of said portionsoutwardly with respect to the central axis of said outlet in the form ofa hollow cone, said means comprising a series of concentric inner andouter annular vanes successively spaced from said outlet and axiallyadjustable as a group relative to said outlet, said series including atleast one outer vane terminating in free inner and outer circumferentialedges and being formed in the nature of a truncated cone having its apexat the side toward said outlet to provide a vane of continuously flaringformation throughout its width from the inner of said edges to theouter, said inner edge being of diameter less than the maximum diameterof said outlet, said series including a single inner vane longitudinallydisplaced from said outlet a greater distance than any outer vane ofsaid series and presenting an exterior surface of truncated conicalformation toward said outlet for deflecting the innermost of saidannular fuel portions, said inner vane terminating in a free outercircumferential edge and its said deflecting surface flaring outwardlyto said edge from an inner circumference substantially equal to theinner circumference of said annular stream of discharging fuel, saidouter edges of said vanes being of progressively decreasing diameters atprogressively increasing distances from said outlet, each of said vanesbeing relatially equal to the inner circumference of said antivelynarrow with respect to its mean diameter and successive vanes beingarranged in overlapping relation to form a compact series of said 'vanesextending longitudinally a distance less and means opposite said nozzleoutlet and within said port for dispersing said fuel into thesurrounding annular body of said combustion air,

said dispersing means comprising a series of spaced inner'and outerannular vanes of frustoconical formation arranged concentrically innested relation, each of said vanes being formed relative to a vertex atthe side toward said nozzle and terminating in a free outercircumferentialedge at the side remote from said nozzle, said seriesincluding outer annular vanes terminating in free inner circumferentialedges at the side toward said nozzle, said free inner edges havingdiameters less than the maximum diameter of said annular outlet andprogressively smaller atv progressively greater distances from saidoutlet,

said series including a single inner vane longitudinally displaced fromsaid outlet a, greater distance than any outer vane of said series andextending in width inwardly toward the central axis of said series atleast to a circumference substannular outlet, said series of nestedvanes extending axially from said nozzle outlet a distance less than the'distance between said outlet and the furnace end of said fuel burnerport.

11. In a fluent fuel burner, a burner tube having an end outletsymmetrically formed about the longitudinal axis of said tube andarranged to discharge fuel in a hollow stream, means for directingcombustion air. longitudinally of said tube in a hollow streamsurrounding said outlet, and means for dispersing said fuel into saidair comprising concentric inner and outer vanes coaxially arranged withrespect to said outlet and successively spaced therefrom, each of saidvanes being of continuous formation about said axis and flaringoutwardly to a free outer edge of a perimeter corresponding inconfiguration and symmetry to the outer perimeter of said outlet, saidfree outer edges being disposed at'progressively decreasing distancesfrom said axis at progressively increasing distances from said outlet,said vanes in-' cluding at least one outer vane terminating in a freeinner edge of smaller perimeter than the outer perimeter of said outletfor dividing said fuel stream into concentric .portions, said inner vaneextending inwardly toward said axis to a perimeter substantially equalin size and'shape to the inner perimeter of said outlet, each of saidvanes being relatively narrow with respect to its average transversedimension and successive vanes being arranged in overlapping relation toform a compact group extending longitudinally a distance less than thanthe average

